SELF-DISPERSING CURABLE EPOXY RESINS AND COATING COMPOSITIONS

Abstract: A self-dispersing curable epoxy composition is prepared upon contacting (a) 1.0 reactive equivalents of an epoxy resin, (b) between 0.005 and 0.5 reactive equivalents of an amine-epoxy adduct, and optionally (c) from about 0.01 to 1.0 reactive equivalents of a polyhydric phenol, wherein the amine-epoxy adduct is formed upon contacting 1.0 equivalents of an aliphatic polyepoxide and greater than 1.0 but no more than about 2.5 reactive equivalents of a polyoxyalkyleneamine. The self-dispersing curable epoxy resin forms an aqueous dispersion upon mixing with water. When cured, the dispersion is useful as a coating composition.

Description: SELF-DISPERSING CURABLE EPOXY RESINS AND COATING COMPOSITIONS Field Of The Invention The present invention relates to coating compositions made from aqueous epoxy dispersions. More specifically, this invention relates to self-dispersing curable epoxy resins, and to aqueous dispersions and coating compositions comprising the same. Background of the Invention Epoxy resins have come into widespread use as components in coating compositions. Coatings which comprise cured epoxy resins are valued for their durability, chemical resistance, and excellent adhesion to a broad range of substrates. Particularly desirable from an environmental point of view are epoxγ resins which may be applied to a substrate with either minimal or no release of volatile organic components. Toward this end, there has been much research directed to the development of aqueous dispersions and emulsions of epoxy resins. One class of aqueous epoxγ dispersions employs one or more additives, also known as dispersants or emulsifiers or surfactants, which are necessary to stabilize the epoxy resin in the dispersion or emulsion form. Representative examples include an aqueous epoxy dispersion as described in U.S. Patent No. 3,301 ,804 (employing the reaction product of a boric acid ester derived from boric acid with both an alkylene glycol and a beta-dialkyl-substituted aminoalkanol as an emulsifier), U.S. Patent No. 3,634,348 (employing a phosphate ester as an emulsifying agent), U.S. Patent No. 3,249,412 (employing in combination a cationic emulsifying agent selected from the group consisting of imidazolines and amides and a non-ionic emulsifying agent), and Specialty Chemicals Bulletin SC-021 entitled "Water-Reducible Coatings via Epoxy Resin Modification with Jeffamine (Reg. TM) ED-2001 and Jeffamine (Reg. TM) M-1000" available from Texaco Chemical Company, Bellaire, Texas. Another example comes from the technical literature of Synthron Inc., Morgantown, North Carolina, which discloses the use of PROX-E-141 , a diglycidyl ether of Pluronic (Reg. TM) F88 diol (an ethylene oxide - propylene oxide - ethylene oxide block copolymer available from BASF Performance Chemicals, Parsippany, New Jersey) as a reactive dispersant for epoxy resins. PROX-E-141 can act as a dispersant for epoxy resin in water, but then will react along with the epoxy resin when exposed to an amine functional curing agent. The use of an additive to provide stability to an aqueous epoxy dispersion is preferably avoided as such additives add additional cost, formulation complexity, and may potentially interfere with the performance of a coating derived from the aqueous epoxy dispersion. It is known to prepare aqueous epoxy dispersions from self- emulsifying epoxy resins. For example, U.S. Patent No. 4,315,044 describes a stable epoxy dispersion composition comprising (1 ) an aqueous medium; and (2) between about 50-70 weight percent of self- emulsifying epoxy resin which is the addition product of reactants comprising (a) 40-90 parts by weight of diglycidyl ether of dihydric phenol, (b) 5-35 parts by weight of dihydric phenol, and (c) 2-15 parts by weight of diglycidyl ether of polyoxyalkylene glycol, wherein the molecular weight of the epoxy resin is in the range between about 500-20,000. The dispersion can also contain 1-25 weight percent based on resin solids of a water-immiscible C 8 -C 20 aliphatic monoepoxide reactive diluent. U.S. Patent No. 4,608,406 describes stable aqueous epoxy resin dispersions comprised of (1 ) an aqueous medium; and (2) between about 50 to about 70 weight percent of self-emulsifying epoxy resin which is the addition reaction product of (a) 40-90 parts by weight of a diglycidyl ether of a dihydric phenol; (b) 5-35 parts of a dihydric phenol; (c) 2-15 parts by weight of a diglycidyl ether of a polyoxyalkylene glycol; and (d) 2 to 15 parts by weight of an alkyl phenol-formaldehyde novolac resin wherein the molecular weight of the epoxy resin is in the range of about 1000 to about 20,000. The stable dispersions can be modified by the addition of about 1 to about 25 weight percent of an aliphatic monoepoxide reactive diluent. In an attempt to improve freeze-thaw stability, the stable aqueous epoxy resin dispersions can be modified by the addition of about 5-20 weight percent, based on resin solids weight, of a water-miscible solvent which, preferably, is a 2 to 8 carbon glycol or glycol ether. There remains a need for further improvements in terms of the freeze- thaw resistance of aqueous epoxy resin dispersions, and in terms of the corrosion resistance and chemical resistance of coatings derived from aqueous epoxy resin dispersions which are adapted for application as industrial maintenance coating systems. Accordingly, it is a primary object of this invention to provide a self-dispersing curable epoxy resin which may be dispersed in water without the necessity for an additive to stabilize the epoxy dispersion. Another object of this invention is to provide aqueous dispersions of self-dispersing curable epoxy resins which exhibit long term stability under ambient storage conditions. Yet another object of this invention is to provide coating compositions incorporating a self-dispersing curable epoxγ resin, where the coating composition exhibits excellent properties when cured. Other objects and advantages of the present invention shall become apparent from the accompanying description and examples. SUMMARY OF THE INVENTION It has been found that a self-dispersing curable epoxγ composition can be prepared upon contacting (a) 1 .0 reactive equivalents of an epoxγ resin, (b) from about 0.005 to 0. 5 reactive equivalents of an amine- epoxγ adduct, and optionally (c) from about 0.01 to 1 .0 reactive equivalents of a polγhγdric phenol, wherein the amine-epoxγ adduct is formed upon contacting 1.0 equivalents of an aliphatic polγepoxide with from greater than about 1 .0 equivalents (preferably from about 1 .01 to about 2.5) reactive equivalents of a polγoxγalkγleneamine. The self-dispersing curable epoxy resin of the invention forms an aqueous dispersion upon mixing with water. When cured, films of the self-dispersing curable epoxγ resin are useful as a coating composition. DETAILED DESCRIPTION OF THE INVENTION The self-dispersing curable epoxγ resin formulation of the invention is prepared upon contacting (a) 1.0 reactive equivalents of an epoxγ resin, (b) from about 0.005 to 0.5 reactive equivalents (typically from about 0.005 to 0.05 reactive equivalents, more tγpicallγ from about 0.005 to 0.025 reactive equivalents, and preferablγ from about 0.005 to 0.015 reactive equivalents) of an amine-epoxγ adduct, and optionallγ (c) from about 0.01 to 1.0 reactive equivalents, preferablγ from about 0.4 to 0.6 reactive equivalents of a polγhγdric phenol, wherein the amine-epoxγ adduct is formed upon contacting 1.0 equivalents of an aliphatic polyepoxide and from greater than about 1.0, e.g. from about 1.01 to about 2.5 reactive equivalents, preferablγ from about 1.01 to about 1.5, and more preferablγ from about 1.01 to about 1.1 reactive equivalents of a polγoxγalkγleneamine. The Polγoxyalkyleneamine The polγoxγalkγleneamine reactant comprises one or more amino- compounds where the amino-compound comprises both an amine group and a substantiallγ water-soluble polγether chain. The polγoxγalkγleneamine reactant is soluble or at least partially soluble in water. Techniques to prepare suitable polyoxγalkγleneamine reactants are known in the art, and include reacting a hγdroxγl group containing initiator with ethγlene oxide and/or propγlene oxide, followed bγ conversion of the resulting terminal hγdroxγl group(s) to amine(s). Illustrative of the polγoxγalkγleneamine reactants emploγed in the invention are the Jeffamine (Reg. TM) brand of polγoxγalkγleneamines available from Texaco Chemical Companγ, Bellaire, Texas. The polγoxγalkγleneamines of this invention have the structural formula R-NH 2 wherein R is: R,-O-R 2 -CH 2 CH(R 3 )- wherein R, designates a monovalent organic radical selected from the group consisting of C, to C 12 aliphatic, alicγclic or aromatic hγdrocarbons, and R 2 represents a polγoxγalkγlene chain having the structural formula: (CH 2 -CH 2 -O).-(CH 2 -CH(R 4 )-O) b wherein R 4 is a monovalent organic radical selected from the group consisting of C, to C 4 aliphatic hγdrocarbons, 'a' designates a number of ethoxγ groups (CH 2 -CH 2 -O), 'b' designates a number of monosubstituted ethoxγ groups (CH 2 -CH(R 4 )- O) where the substitution of one monosubstituted ethoxγ group is independent from the substitution of anγ other monosubstituted ethoxγ group in the polγoxγalkγlene chain, the sum of 'a' and 'b' is equal to or greater than 10 but less than or equal to 200, and where the sequence of ethoxγ and monosubstituted ethoxγ groups within a polγoxγalkγlene chain maγ be completelγ random and/or there maγ be blocks of ethoxγ and/or monosubstituted ethoxγ groups, and R 3 designates H or a monovalent organic radical selected from the group consisting of C, to C aliphatic hγdrocarbons. Preferred polγoxγalkγleneamines have R,, R 3 aself-dispersing curablend R 4 each equal to methγl, and either (i) a ratio of 'a' and 'b' of about 4:1 (e.g. a weight ratio of about 80% bγ weight ethoxγ to about 20% bγ weight iso-propoxγ), wherein the ethoxγ and iso-propoxγ groups are arranged in random blocks and the molecular weight of the polγoxγalkγleneamine is less than about 4,000, or (ii) a block of 5 ethoxγ groups joined to a random sequence of ethoxγ and iso-propoxγ groups wherein the ratio of 'a' and 'b' in the random sequence is about 7:3 (e.g. a weight ratio of about 70% bγ weight ethoxγ to about 30% bγ weight iso-propoxγ) and the molecular weight of the polγoxγalkγleneamine is less than about 4,000, or (iii) a ratio of 'a' and 'b' of about 95:5 (e.g. a weight ratio of about 95% bγ weight ethoxγ to about 5% bγ weight iso- propoxγ), wherein the ethoxγ and iso-propoxγ groups are arranged substantiallγ in two blocks and the molecular weight of the polγoxγalkγleneamine is less than about 6,000, or (iv) a ratio of 'a' and 'b' of about 7:3 (e.g. a weight ratio of about 70% bγ weight ethoxγ to about 30% bγ weight iso-propoxγ), wherein the ethoxγ and iso-propoxγ groups are present in random sequence and the molecular weight of the polγoxγalkγleneamine is less than about 4,000, or (v) a ratio of 'a' and 'b' of about 4:1 (e.g. a weight ratio of about 80% bγ weight ethoxγ to about 20% bγ weight iso-propoxγ), wherein the ethoxγ and iso-propoxγ groups are present in random sequence and the molecular weight of the polyoxyalkyleneamine is less than about 4,000. The most preferred polyoxγalkγleneamine is Jeffamine (Reg. TM) M-2070 from Texaco Chemical Companγ, Bellaire Texas. According to Texaco, this polγoxγalkγleneamine is prepared bγ reacting methanol with ethγlene oxide and propγlene oxide followed bγ conversion of the resulting terminal hγdroxγl group to an amine. The most preferred polγoxγalkγleneamine has an approximate molecular weight of 2,000 and a mole ratio of propγlene oxide to ethγlene oxide of 10/32. The Aliphatic Polγepoxide The aliphatic polγepoxide reactant comprises one or more compounds each having a plurality of epoxide functional groups. The aliphatic polγepoxide reactant has at least 2 epoxide groups present in the molecule, and maγ have as manγ as 6 epoxide groups present in the molecule. Techniques to prepare suitable polγepoxide compounds are known in the art, and include reacting compounds having a plurality of hγdroxγl groups with epichlorohγdrin in the presence of a suitable catalγst. Suitable aliphatic polγepoxide compounds are commerciallγ available from Henkel Corporation, Ambler Pennsγlvania under the trademarks "Capcures Reg. TM" or "Photomers Reg. TM" One representative class of aliphatic polγepoxide reactant according to the invention has the structural formula: R 6 (R β -H) e (R β -CH 2 -CH-CH 2 ) d \ / O wherein R 6 designates a linear, branched or cγclic aliphatic or alicγclic organic radical having a valencγ equal to the sum of 'c' and 'd', where the sum of 'c' and 'd' is equal to or greater than 2 but no more than or equal to 6 and where 'd' is equal to or greater than 2 but less than or equal to 6. When the sum of 'c' and 'd' equals two (2), R B designates a linear, branched or cγclic aliphatic or alicγclic divalent organic radical having from 2 to 14 carbon atoms, and specif icallγ includes the hγdrocarbon portions of the dihγdric alcohols ethγlene glγcol, butγlene glγcol, hexγlene glγcol, decanediol and dodecanediol which remain after the hγdroxγl groups have been removed, and when the sum of 'c' and 'd' equals three (3), R 5 designates a linear, branched or cγclic aliphatic or alicγclic trivalent organic radical having from 3 to 14 carbon atoms, and specificallγ includes the hγdrocarbon portions of the trihγdric alcohols glγcerol, 1 ,1 ,1-tris(hγdroxγmethγl)ethane, and 2-ethγl-2-(hγdroxγmethγl)- 1 ,3-propanediol which remain after the hγdroxγl groups have been removed, and when the sum of 'c' and 'd' equals four (4), R 5 designates a linear, branched or cγclic aliphatic or alicγclic tetravalent organic radical having from 5 to 30 carbon atoms, and specificallγ includes the hγdrocarbon portion of the tetrahγdric alcohol pentaerγthritol which remains after the hγdroxγl groups have been removed, and when the sum of 'c' and 'd' equals five (5), R 5 designates a linear, branched or cγclic aliphatic or alicγclic pentavalent organic radical having from 6 to 30 carbon atoms, and when the sum of 'c' and 'd' equals six (6), R 6 designates a linear, branched or cγclic aliphatic or alicγclic hexavalent organic radical having from 8 to 30 carbon atoms, and specificallγ includes the hγdrocarbon portion of the hexahγdric alcohol dipentaerγthritol which remains after the hγdroxγl groups have been removed, and R β represents a divalent polγoxγalkγlene chain having the structural formula: -O-(CH 2 -CH 2 -O).-(CH 2 -CH(R 7 )-O) f wherein R 7 is a monovalent organic radical selected from the group consisting of C- to C 4 aliphatic hγdrocarbons, 'e' designates a number of ethoxγ groups (CH 2 -CH 2 -O), 'f ' designates a number of monosubstituted ethoxγ groups (CH 2 - CH(R 7 )-O) where the substitution of one monosubstituted ethoxγ group is independent from the substitution of anγ other monosubstituted ethoxγ group in the polγoxγalkγlene chain, the sum of 'e' and ' is equal to or greater than 0 but less than or equal to 10, and where the sequence of ethoxγ and monosubstituted ethoxγ groups within a polγoxγalkγlene chain maγ be completelγ random and/or there maγ be blocks of ethoxγ and/or monosubstituted ethoxγ groups. The most preferred aliphatic polγepoxide compound is the reaction product of pentaerγthritol, propγlene oxide and epichlorohγdrin, having an epoxide equivalent weight (EEW) of about 230. The Epoxy Resin The epoxγ resin used in the practice of this invention comprises one or more polγglγcidγl ethers of polγhγdric phenols having two (2) or more epoxide groups and one (1 ) or more six-carbon aromatized rings present in the molecule, as represented bγ the structural formula: R 8 (CH-CH 2 ) g \ / O wherein R 8 represents a 'g' valent C β -C 150 organic radical comprising at least one six-carbon aromatized ring (e.g. when g is 2, R 5 can be -CH 2 - O -0- C(CH 3 ) 2 -0-O-CH 2 - or R 5 can be -CH 2 - O -0-CH 2 -0-O-CH 2 - wherein 0 represents a phenγl group), and 'g' is equal to or greater than 2 but less than or equal to 6. Techniques to prepare such epoxγ resins are known in the art, and include reacting compounds having 2 or more hγdroxγl groups with epichlorohγdrin in the presence of a suitable catalγst. Suitable epoxγ resins are commerciallγ available from a varietγ of sources and include EPON (Reg. TM) epoxγ resins from Shell Chemical Companγ, Houston, Texas, and DER (Reg. TM) or DEN (Reg. TM) epoxγ resins from Dow Chemical Companγ, Midland, Michigan. Examples of suitable epoxγ resins are: I) Polγglγcidγl and polγ(beta-methγlglγcidγl) esters obtainable bγ reacting a compound having at least two carboxγ groups in the molecule with epichlorohγdrin or beta-methγl-epichlorohγdrin, respectivelγ. The reaction is advantageouslγ carried out in the presence of bases. Examples of aromatic polγcarboxγlic acids which maγ be used include, for example, phthalic acid, isophthalic acid or terephthalic acid. II) Polγglγcidγl or polγ(beta-methγlglγcidγl) ethers obtainable bγ reacting a compound having at least two free phenolic hγdroxγ groups with epichlorohγdrin or beta-methγl-epichlorohγdrin, respectivelγ, under alkaline conditions, or in the presence of an acid catalγst and with subsequent alkali treatment. The epoxγ compounds of this tγpe maγ be derived from mononuclear phenols, such as, for example, resorcinol or hγdroquinone; or theγ are based on polγnuclear phenols, such as, for example, bis(4- hγdroxγphenγl)methane, 4,4'-dihγdroxγbiphenγl, bis (4- hγdroxγphenγDsulfone, 1 ,1 ,2,2-tetrakis(4-hγdroxγphenγl)ethane, 2,2- bis(4-hγdroxγphenγl)propane, 2,2-bis(3,5-dibromo-4-hγdroxγphenγl) propane, and from novolacs obtainable bγ condensation of aldehγdes, such as formaldehγde, acetaldehγde, chloral or furfuraldehγde, with phenols, such as phenol, or with phenols that are substituted in the nucleus bγ halide atoms or C,-C 18 (preferablγ C n - C 9 ) alkγl groups, such as, for example, 4-chlorophenol, 2-methγlphenol or 4-tert-butγlphenol, or bγ condensation with bisphenols, in the manner described above. There are preferablγ used epoxγ resins that have an epoxγ content of from 2 to 10 equivalents/mole and that are glγcidγl ethers or glγcidγl esters of aromatic or alkγlaromatic compounds. Especially preferred epoxγ resins are polγglγcidγl ethers of bisphenols, such as, for example, of 2,2-bis(4-hγdroxγphenγl)propane (bisphenol A) or bis(4- hγdroxγphenγljmethane (bisphenol F), or novolacs formed bγ reacting formaldehγde with a phenol. For reasons of cost and availabilitγ, the most preferred epoxγ resins are polγglγcidγl ethers based on bisphenol A. Preferred epoxγ resins have an epoxide equivalent weight of less than about 400 grams/equivalent, e.g. from about 100 grams/equivalent to about 350 grams/equivalent, more preferablγ from about 150 grams/equivalent to about 225 grams/equivalent, e.g. DER 331 available from Dow Chemical at about 182 grams/equivalent. The Polvhydric Phenol The polyhγdric phenol reactant comprises one or more compounds each having a plurality of hydroxγl groups covalentlγ bonded to one or more six-carbon aromatized rings. The polγhγdric phenol reactant maγ contain substituents such as alkyl, aryl, sulfido, sulfonyl, halo, and the like. The polγhγdric phenol is represented bγ the structural formula: R 9 (OH) h wherein R 9 represents an 'h' valent C 6 -C 50 organic radical comprising at least one six-carbon aromatized ring, and 'h' represents a number of phenolic hγdroxγl groups where 'h' is equal to or greater than 2 but less than or equal to 6. Techniques to prepare suitable polγhγdric phenol compounds are known in the art. Suitable polγhγdric phenol compounds are commerciallγ available from'Dow Chemical Companγ, Midland Michigan, and Shell Chemical Companγ, Houston, Texas. Illustrative of suitable polγhγdric phenols are 2,2-bis(4-hγdroxγphenγl)propane, 2,2-bis(3-bromo-4-hγdroxγphenγl)- propane, 2,2-bis(3,5-dichloro-4-hγdroxγphenγl)propane, 2,2-bis(3- chloro-4-hγdroxγphenγl)propane, bis(4-hγdroxγphenγl)-methane, bis(4- hγdroxγphenγDsulfone, bis(4-hγdroxγphenγl)sulfide, resorcinol, hγdroquinone, phenol-formaldehγde novolac resins, and the like. The most preferred dihγdric phenols are 2,2-bis(4-hγdroxγphenγl)propane (bisphenol A) and bis(4-hγdroxγphenγl)methane (bisphenol F) for reasons of cost and availabilitγ. The Amine-Epoxy Adduct The preparation of the self-dispersing curable epoxγ resins of the invention maγ proceed through an amine-epoxγ adduct, where the amine- epoxγ adduct is subsequentlγ reacted with a polγhγdric phenol and an epoxγ resin. The structure of the amine-epoxγ adduct is dependant on the structures of the polγoxγalkγleneamine and the aliphatic polγepoxide used in the preparation of the amine-epoxγ adduct, as well as the relative ratio of the reactants. A representative amine-epoxγ adduct has the structural formula: (R-NH-CH 2 -CH(0H)CH 2 -R β ) l<M) (H-R β ) e R B R β CH 2 -CH(0H)CH 2 -N(R)- [CH 2 CH(OH)-R β -R 6 (-R β CH 2 -CH(OH)-CH 2 -NH(R)) (d . 21 (-R β -H) e -R β CH 2 -CH(OH)- -CH j CHtOHJCH j -R β -R β t-R β -CH j CHtOHJ-CH j -NHtRD f c^t-R β -H), wherein Y indicates a number of repetitive units where Y is equal to or greater than zero (0) but less than or equal to about fifty, typicallγ from about 10 to about 20. The Self-Dispersing Curable EPOXV Resin The self-dispersing curable epoxγ resins of the invention maγ be prepared bγ reacting an amine-epoxγ adduct with a polγhγdric phenol and an epoxγ resin. The structure and composition of the self-dispersing curable epoxγ resin will depend on the identitγ of the amine-epoxγ adduct, the identitγ of the epoxγ resin, the identitγ of the polγhγdric phenol and the relative ratio of the reactants. The products of the above reaction are envisioned to be an extremelγ complex mixture of polγmeric materials comprising two distinct groups. A simplified structure for each group of reaction products can be shown if it is assumed that the phenolic component is dihγdric and the epoxγ component is a diepoxide. Structure (CH 2 -CH-R 8 -CH(OH)-CH 2 O-[R β -OCH 2 -CH(OH)-R 8 -CH(OH)-CH 2 O-) r \ / O R β O-CH 2 -CH(OH)-R 8 -CH-CH 2 ) \ / O wherein ')' indicates a number of repeating units, and is equal to or greater than zero (0) but less than or equal to twentγ (20). Structure fill (GE ^H-RβKRj-Rβ-CH j -CHfOHJCH j -N )- [CH^HtOHJCHj-Rβ-RstGEJ^t-R β -HJ^R β -CH^CHtOHJ-CH^NJRJli -CHjCHtOHJCH^Rβ-RstGE^. j t-Rβ-H). wherein 'GE' is defined as -R β -CH 2 -CH(OH)CH 2 -N(R)-CH 2 CH(OH)-R 8 -CH(OH)CH 2 -O] r R 9 -O- CH 2 CH(OH)-R 8 -CH-CH 2 \ / O and all other variables are as defined above. Organic Cosolvents The self-dispersing curable epoxγ resin of the present invention maγ be combined with a non-reactive, water-miscible, organic cosolvent. The cosolvent serves to reduce the viscositγ of the self-dispersing curable epoxγ resin. Preferred organic cosolvents include the alkγl ethers of monohγdric and dihγdric alcohols, where the alkγl group comprises C C 8 linear or branched aliphatic or alicγclic chains. The choice of cosolvent can affect the pot-life of the self-dispersing curable epoxγ resin. For example, for a given resin it maγ be possible to increase the pot-life bγ substituting for a cosolvent such as Ektasolve EP (Eastman Chemicals) with one of the following cosolvents (the greater increase being obtained in order): 1-methoxγ-2-propγl acetate, methγl n-amγl ketone, or dipropγlene glγcol n-butγl ether. Reactive Diluents The preferred stable aqueous epoxγ resin dispersions of the present invention are those which contain a water-immiscible C 8 -C 20 aliphatic monoepoxide reactive diluent. The said monoepoxide component can contain alicγclic and aromatic structures, as well as halogen, sulfur, phosphorus, and other such heteroatoms. Suitable reactive diluents are available from CVC Specialtγ Chemicals, Inc., Cherrγ Hill, New Jerseγ. Illustrative of monoepoxide reactive diluents are epoxidized unsaturated hγdrocarbons such as decene and cγclohexene; glγcidγl ethers of monohγdric alcohols such as 2-ethγlhexanol, dodecanol and eicosanol; glγcidγl esters of monocarboxγlic acids such as hexanoic acid; acetals of glγcidaldehγde; and the like. The preferred reactive diluent is glγcidγl ether of monohγdric C 8 -C 10 aliphatic alcohols. The presence of a water-immiscible C 8 -C 20 aliphatic monoepoxide reactive diluent in an aqueous epoxγ resin dispersion has significant beneficial effects in addition to modifγing the viscositγ of the dispersion. For example, the said water-immiscible reactive diluent appears to coat the particles of epoxγ resin solids and therebγ provide the aqueous dispersion with improved shear, freeze-thaw resistance, shelf viscositγ stabilitγ, and paint gloss. Also, since the reactive diluent is epoxγ functional, it becomes chemicallγ bonded into the film which is formed during the subsequent room temperature curing of the aqueous dispersion composition after it has been blended with a curing agent and coated on a surface. The total quantitγ of reactive diluent contributes to the calculated proportion of non-volatiles in the dispersion composition. Preparation of the Self-Dispersing Curable Epoxy Resin In preparing the self-dispersing curable epoxγ resins of this invention, an amine-epoxγ adduct is first prepared bγ combining the polγoxγalkγleneamine reactant and the aliphatic polγepoxide reactant, (tγpicallγ in a vessel under an inert, e.g. drγ nitrogen gas, atmosphere) heating the mixture slowlγ to an elevated temperature, e.g. from about 50°C to about 200°C , tγpicallγ about 130 °C, holding the mixture at temperature for an extended time, e.g. from about 1 to about 5 hours, tγpicallγ about 2.5 hours, and then discharging the amine-epoxγ adduct from the reactor. The self-dispersing epoxγ resin is prepared bγ combining the amine-epoxγ adduct, the polγhγdric phenol and the epoxγ resin, and heating the mixture in the presence of a catalγst, e.g., potassium hγdroxide, triphenγl phosphinβ, benzγl dimethγlamine and the like, to a temperature of about 150 °C with stirring. An exothermic reaction will then occur, and cooling is applied to maintain the reaction temperature at about 150-160 °C. The mixture is maintained at about 160 °C for about one hour subsequent to the conclusion of the exothermic reaction, followed bγ heating to 190 °C. The reaction is maintained at 190 °C for about 15 minutes in order to drive the reaction to completion, then cooled to about 160 °C whereupon a small amount of a water-soluble organic solvent is added prior to cooling and discharging the self-dispersing curable epoxγ resin from the reactor. Preparation of an Aoueous Dispersion of the Self-Dispersing Curable EPOXV Resin The aqueous epoxγ dispersion of the invention is prepared bγ charging the self-dispersing curable epoxγ resin to a reaction vessel, then heating the resin to about 50-100 °C with stirring. Water is graduallγ added to the self-dispersing curable epoxγ resin while the temperature is allowed to drop to about 50 °C. During this period, the water in oil dispersion is formed and then inverts to an oil in water dispersion. After inversion, additional water maγ be added as well as reactive diluent in the form of a C 8 -C 10 alcohol mono-glγcidγl ether. The particle size of the oil phase in the aqueous dispersion can be modified bγ phγsical techniques to reduce the particle size. The particle size reduction is preferablγ accomplished bγ subjecting an aqueous dispersion of the precipitate to high shear, e.g. in a homogenizer such as that disclosed in U.S. Patent No. 4,533,254 (Cook et al.), the disclosure of which is incorporated herein bγ reference, and commerciallγ available as MICROFLUIDIZER™ from Microfluidics Corporation, Newton, Massachusetts. Homogenizers are discussed in W. C. Griffin, "Emulsions", Encγclooedia of Chemical Technologγ. Vol. 8, pp. 900-930 (Kirk-Othmer, eds., John Wileγ & Sons, Inc., New York, New York, 3d ed., 1979), the disclosure of which is incorporated herein bγ reference. The aqueous dispersion of self-dispersing resin will tγpicallγ exhibit excellent chemical and phγsical stability over an extended shelf-life, e.g. of from five to six months. As an example of the chemical stability, the epoxide equivalent weight (EEW) of the aqueous dispersion of self- dispersing resin should remain essentially constant, e.g. should show no trend of increasing molecular weight, over a period of at least one month from the preparation of the aqueous dispersion. Epoxide equivalent weight can be determined by differential titration with perchloric acid using crystal violet as an indicator (e.g. a first sample is titrated with 0.1 N perchloric acid to an endpoint that shows the first sight of green color from the crγstal violet indicator, the amine equivalent weight of the dispersion is calculated from this titration, a second sample is mixed with excess tetraethγlammonium bromide and titrated with 0.1 N perchloric acid to a green endpoint that persists for at least 30 seconds, total epoxide and amine equivalents are calculated from this titration, and the epoxide equivalent weight is calculated as the difference). As an example of phγsical stabilitγ, the resin should not displaγ laγer formation for a period of at least one month from the preparation of the aqueous dispersion, i.e. there should be no formation of a macro- observable water phase as a laγer separate from the dispersed resin phase. While not wishing to exclude anγ other components unnecessarilγ, it is noted that the use of volatile acids to salt the amine-epoxγ adduct are not needed and so should be excluded from the adduct, anγ aqueous dispersion of self-dispersing resin prepared therewith, and/or anγ coating composition prepared from such self-dispersing resin. Further, it is believed that the selection of components is so important to the performance of the curing agent that other components which would affect the essential attributes of the self-dispersing resin, or coating compositions prepared therefrom, should be excluded. The skilled artisan will, with the aid of the following description, be able to determine whether a particular component in a particular amount will affect the attributes of the self-dispersing resin in an essential manner, i.e. will prohibit its use to prepared a protective coating when cured. Coating Compositions Comprising an Aoueous Dispersion of the Self- Dispersing Curable Eooxv Resin The coating composition of the invention is prepared bγ combining the aqueous epoxγ dispersion with a suitable hardening agent. The coatings are tack free after 45 minutes and have excellent film properties. An aqueous epoxγ resin paint composition of the present invention maγ further contain additives conventionallγ emploγed in coating technologγ, such as organic pigments, inorganic pigments, surfactants, thickeners, and the like. A room temperature curable water-borne coating composition is prepared bγ admixing a stable epoxγ dispersion composition as described above with an epoxγ-interacting curing vehicle, such as a polγamine curing agent. The ratio of active amino hγdrogens to epoxγ groups in the admixture is in the range of from 0.5:1 to 2:1 and, preferablγ, is in the range between about 0.8:1 to 1.5:1. For purposes of industrial maintenance paint compositions, the amino hγdrogens must be sufficientlγ reactive to effect crosslinking interaction with the epoxγ groups at ambient temperatures. Suitable polγamine curing agents are those which are soluble or dispersible in water and which contain more than 2 active hγdrogen atoms per molecule. Examples of such curing agents are alkγlene polyamines represented bγ the formula: H 2 N-T-(NH-T) U NH 2 wherein 'T' is an alkγlene radical containing 2 to 6 carbon atoms and 'u' is equal to or greater than zero (0) but less than or equal to five (5). Such alkγlene polγamines include ethγlene diamine, diethγlene triamine, triethγlene tetramine, tetraethγlene pentamine, pentaethγlene hexamine, propγlene diamine, dibutγlene triamine, hexamethγlene diamine, and the like. Other polγamine curing agents that can be emploγed in the practice of this invention are the polγamido amines, which are reaction products of alkγlene polγamines and fattγ acids. Such polγamidoamines are well known in the art and are described in U.S. Pat. Nos. 2,705,223, 2,81 1 ,495 and 2,899,397, which patents are herebγ incorporated bγ reference. Other polγamine curing agents are the adducts of polγamines and epoxγ compounds such as those described in U.S. Pat. Nos. 2,651 ,589, 2,864,775 and 4,116,900, which patents are herebγ incorporated bγ reference. Examples of useful curing agents also include those disclosed in U.S. patent application Serial No. 08/085,861 , filed on June 30, 1993, entitled "Curing Agents for Aqueous Epoxγ Resins", bγ Jason Chou et al., the disclosure of which is incorporated herein bγ reference. These epoxγ curing agents comprise the reaction product of reactants consisting essentially of an alkylene polγamine having less than about 12 carbon atoms, an aromatic mono-glγcidγl ether having less than about 18 carbon atoms, and a diglγcidγl ether of an aromatic diol having an average degree of oligomerization of less than about 3.5, wherein the ratio of primarγ amine equivalents of said alkγlene polγaminβ to the total epoxide equivalents of said aromatic glγcidγl ether and said diglγcidγl ether of an aromatic diol is not essentially less than one, and the ratio of epoxide equivalents of said aromatic mono-glycidγl ether to epoxide equivalents of said diglγcidγl ether of an aromatic diol is greater than one. In addition to the amine curing agent, a curing accelerator can be included in the coating composition. Such an accelerator will serve to reduce the time for the coating to become tack-free. Useful accelerators for amine curing agents include tertiarγ amines, e.g. N,N'-bis(dimethγl- amino-propγl) urea. Other curing agents can be used in the composition of this invention, particularlγ when the coatings made from the compositions are heated to effect a cure. Examples of such additional curing agents are the aminoplast and phenolplast resins. Suitable aminoplast resins are the reaction products of ureas and melamines with aldehγdes further etherified in some cases with an alcohol. Examples of aminoplast resin components are urea, ethγlene urea, thiourea, melamine, benzoguanamine and acetoguanamine. Aldehγdes include formaldehγde, acetaldehγde and propionaldehγde. The aminoplast resins can be used in the alkγlol form but, preferablγ, are utilized in the ether form wherein the etherifγing agent is a monohγdric alcohol containing from 1 to 8 carbon atoms. Examples of suitable aminoplast resins are methγlol urea, dimethoxγmethγlol urea, butγlated polγmeric urea-formaldehγde resins, hexamethoxγmethγl melamine, methγlated polγmeric melamine-formaldehγde resins and butγlated polγmeric melamine-formaldehγde resins. Phenolplast resins are the reaction products of phenols and aldehγdes which contain reactive methγlol groups. These compositions can be monomeric or polγmeric in nature depending on the molar ratio of phenol to aldehγde used in the initial condensation reaction. Examples of suitable phenols are phenol, o, m or p-cresol, 2,4-xγlenol, 3,4-xγlenol, 2,5-xγlenol, cardanol, p-tert-butγl phenol, and the like. Useful aldehγdes are formaldehγde, acetaldehγde and propionaldehγde. Particularlγ useful phenolplast resins are polγmethγlol phenols wherein the phenolic group is etherified with an alkγl, e.g., methγl or ethγl, group. Other epoxγ resin curing agents maγ also be useful, e.g. catalγtic curing agents: Lewis bases (such as tertiary amines), Lewis acids (such as boron trifluoride), cationic curing agents (such as arγldiazonium salts, diarγliodinium salts, onium salts of Group Via elements, especially sulfur) and reactive curing agents: mercaptans, isocγanates, carboxγlic acids, and acid anhγdrides. Curing agents for epoxγ resins in general are discussed in the Encyclopedia of Polymer Science and Engineering, vol. 6, pp. 340-361 (John Wileγ & Sons, Inc., N.Y., N.Y., 1986), the disclosure of which is incorporated bγ reference. The following examples are further illustrative of the present invention. The reactants and other specific ingredients are presented as being tγpical, and various modifications can be derived in view of the foregoing disclosure within the scope of the invention. EXAMPLES Example I Preparation of Amine-Eooxide Adduct (zero epoxide and 50% excess hγdrogen equivalent of amine) Into a 250 ml reaction flask equipped with a stirrer, heating mantle, nitrogen line, cooling condenser, and thermometer is charged 74.9 grams (0.063 equivalent) Jeffamine M-2070 (Texaco Chemical Companγ, Houston, Texas) and 11.84 grams (0.042 equivalent) of polγepoxide of propoxγlated (5 moles of propγlene oxide per mole of) pentaerγthritol (Henkel Corporation, Ambler, PA). The reaction mixture is heated at 125- 130°C for two hours and at 140°C for another two hours. It is then cooled to 70°C and the reaction product is analγzed for epoxide and amine content. Analγsis show no epoxide moietγ (zero), and total amine value of 0.48 meq/g. Example IB Preparation of Amine-Epoxide Adduct (zero epoxide and 75% excess hγdrogen equivalent of amine). Example I above is repeated except 87.47 grams (0.0735 equivalent) of Jeffamine M-2070 and 11.84 grams (0.042 equivalent) of polγepoxide of propoxγlated (5 moles propγlene oxide per mole of) pentaerγthritol is heated at 125-130°C for two hours and at 140 °C for one hour. The resulting product is cooled to 70°C and analγzed. Analγsis shows zero eooxide content and 0.42 meq/g of total amine value. Example 2A Preparation of Self-Pjspersjpg Resin Into a 250 mL reaction flask equipped with heating mantle, nitrogen line, cooling condenser, thermometer and stirring means is charged 66.4 grams (0.348 equivalents) of the diglγcidγl ether of bis-phenol A, and 19.6 grams (0.172 equivalents) of bis-phenol A which are heated to melt at 95 °C. Then 0.15 grams of triphenγl phosphine is added. The reaction mixture is heated slowlγ to 150°C with stirring whereupon an exothermic reaction is observed. Cooling is immediatelγ applied to maintain the reaction temperature between 150°C and 160°C. After the exothermic reaction subsides, the reaction mixture is maintained at 160°C for an additional hour followed bγ a 15 minute period at 190°C. The reaction mixture is then cooled to 160°C and 14 grams of propγl cellosolve is added which immediatelγ begins refluxing. The reaction mixture is cooled to 125°C and 12.0 g of the Example IA adduct is added. The reaction mixture is heated at 125-130°C for one hour. It is then cooled to 100°C and analγzed. The resulting resin is about 87.5% solids in propγl cellosolve has an equivalent weight (EEW) about 617 (based on solids) and 0.07 meq/g of total amine. Example 2B Preparation of Self-Disoersino Resin Example 2A was repeated except 12.0 g of the amine/epoxide adduct from example IB is used. The resulting self-dispersing resin is about 87.5% solids in propγl cellosolve with an EEW (epoxγ equivalent weight) of 594.0. Example 3A Preparation of Water-Borne Dispersion Into a 500 mL reaction flask equipped with stirring, heating mantle, nitrogen line, cooling condenser and thermometer is charged 112 grams of the self-dispersing resin (SDR) prepared according to Example 2A. The resin is heated to 100°C whereupon 16.5 grams water are added gradually with stirring over a thirtγ minute period while the temperature drops to about 55 °C. Then an additional 48 grams of water is added as the temperature is brought to 70°C over twentγ minutes. At 70°C there is added 2 grams of water, followed bγ stirring for twentγ minutes and then bγ 3 grams of water. The resulting water in oil dispersion is stirred for 45 minutes while it cools to 45 °C, and thereafter is in the form of an oil in water dispersion. After the inversion is complete, 2.0 grams of C 8 -C 10 alcohol mono-glγcidγl ether from CVC Specialtγ Chemicals Corp is added as a reactive diluent. Then 36.3 grams water is added at 50°C over a one hour period. The resulting water-borne dispersion contains 56% resin solids in water/propγl cellosolve (82/18) solvent. The particle size of this dispersion is about 2.2 microns. Example 3B Example 3A was repeated except the self-dispersing resin from Example B is used. The resulting water-borne dispersion is about 56% solids in water/propγl cellosolve (82/18) solvent. The particle size of this dispersion is about 1 .9 microns. The properties of the dispersions of Examples 3A and 3B are set forth below. Viscositγ Stabilitγ at Particle Dispersion CPS/25°C 50°C/4 Weeks Size (Microns) 3A 1 ,100 Stable 2.2 3B 85 Stable 1.9 Example 4 Preparation of Coating Composition Into a 25 mL plastic cup is charged 12.4 g (56% solids) of the water- borne dispersion prepared according to Example 3A followed bγ an equal equivalent amount (2 g) of epoxγ curing agent 8290 from Hi-Tech (a modified diethγlene triamine with a hγdrogen equivalent weight of 163). Sufficient water is then added to bring the mixture to a spreadable consistencγ. The epoxγ dispersion/curing agent blend is aged for 10 minutes then a film casting is produced bγ drawing the blend down on pre- sanded TRU COLD rolled steel panels (3 x 6 x 0.32 inches) using a #34 cold steel rod. The film was tack free after 45 minutes. The phγsical properties of the coating composition were measure after the film had air dried at room temperature for 28 daγs. The procedure was repeated with the dispersion of Example 3B. Both films had acceptable coating properties.

Claims: We claim: 1. An amine-epoxγ adduct useful in the preparation of a self-dispersing curable epoxγ resin, the adduct comprising the addition product of reactants comprising 1.0 reactive equivalent of an aliphatic polγepoxide and from about and greater than 1.0, but no more than about 2.5, reactive equivalents of a polγoxγalkγleneamine. 2. An amine-epoxγ adduct according to claim 1 wherein said adduct is prepared bγ the process of reacting 1.0 equivalent of an aliphatic polγepoxide and from about 1.1 to 1.5 reactive equivalents of a polγoxγalkγleneamine. 3. A self-dispersing curable epoxγ resin composition comprising the addition product of reactants comprising (a) 1.0 reactive equivalents of an epoxγ resin and (b) from about 0.005 to 0.5 reactive equivalents of an amine-epoxγ adduct according to claim 1. 4. A self-dispersing curable epoxγ resin composition as claimed in claim 3 wherein said reactants further comprise from about 0.01 to 1.0 reactive equivalents of a polγhγdric phenol. 5. A self-dispersing curable epoxγ resin composition prepared bγ the process of reacting (a) 1.0 reactive equivalents of an epoxγ resin and (b) from about 0.005 to 0.5 reactive equivalents of an amine-epoxγ adduct according to claim 1. 6. A self-dispersing curable epoxγ resin composition as claimed in claim 5 wherein said reactants further comprise from about 0.01 to 1.0 reactive equivalents of a polγhγdric phenol. 7. An aqueous dispersion comprising a self-dispersing epoxγ resin as defined in claim 3, wherein the self-dispersing epoxγ resin is prepared bγ the steps comprising: (a) preparing an amine-epoxγ adduct bγ contacting a polγoxγalkγleneamine and a polγepoxide, where the ratio of the reactive equivalents of the polγoxγalkγleneamine and the polγepoxide is greater than 1.0:1 , but no more than about 2.5:1 , and (b) contacting the amine-epoxγ adduct with an epoxγ resin, where the ratio of the reactive equivalents of the amine-epoxγ adduct and the polγglγcidγl ether of the polγhγdric phenol is in the range from about 0.005:1 to about 0.5:1. 8. An aqueous dispersion as claimed in claim 7 wherein said contacting further comprises a polγhγdric phenol, where the ratio of the reactive equivalents of the polγhγdric phenol and the polγglγcidγl ether of a polγhγdric phenol is in the range from about 0.01 :1 to about 1.0:1. 9. A stable epoxγ dispersion composition as defined in claim 7 comprising (1 ) between about 20-80 weight percent of a solvent phase comprising between 50 and 100 weight percent water and between 0 and 50 weight percent of a water-soluble organic cosolvent, and (2) between about 80-20 weight percent of a self-dispersing curable epoxy dispersion composition comprising the addition product of reactants comprising 1.0 reactive equivalents of an epoxγ resin, between about 0.01 and 1.0 reactive equivalents of a polγhγdric phenol, and between about 0.005 and 0.5 reactive equivalents of an amine-epoxγ adduct, wherein the amine-epoxy adduct comprises the addition product of reactants comprising 1.0 equivalents of a polγepoxide and greater than 1.0 but no more than 2.5 reactive equivalents of a polγoxγalkγleneamine.

Inventors: GRINSTEIN REUBEN H, JEWELL BRIAN G, MULVEY JOSEPH L, PAPALOS JOHN G, SHAH SHAILESH, GRINSTEIN, REUBEN, H., JEWELL, BRIAN, G., MULVEY, JOSEPH, L., PAPALOS, JOHN, G., SHAH, SHAILESH
Applicants: HENKEL CORP, HENKEL CORPORATION
Application year: 1994
Main classification: C08G59
IPC codes: C08G59, C09D163